The invention relates to electromagnetic interference (EMI) and, more particularly, to the reduction of EMI in magnetic recording/reproduction devices.
Magnetic recording/reproduction devices such as disk drives write information to and read information from a magnetic medium. In the case of disk drives, the information is written to and read from a rotating magnetic disk using a write head, read head, or read/write head which xe2x80x9cfliesxe2x80x9d a very short distance above the disk, cushioned by an air bearing. Read, write, and read/write heads may be referred to hereinafter generically as disk heads, or, simply, heads. Heads often operate in close proximity to one another, sometimes reading and writing simultaneously. This is particularly true in a test center where a number of heads may be tested simultaneously. In such an environment there may be several test stations, each with a disk mounted on a spindle with corresponding read and write heads with technicians operationally testing disk drives, including heads. During a disk write operation, a write head emits electromagnetic interference (EMI) that may interfere with the operation of electronics and/or other heads. The disk upon which data is written may operate as an antenna, gathering EMI from a disk-write operation, from ambient radio or television signals, or from other sources. During the testing process the heads and media are typically exposed. That is, although it might be possible to enclose each test station within a separate xe2x80x9cFaraday cagexe2x80x9d in order to prevent the EMI (generated by a write head under test or another source) from interfering with a head being tested, such a construction would be impractical; particularly in view of the fact that test technicians would be enclosed in such xe2x80x9ccagesxe2x80x9d.
Additionally, in a disk drive application, the electromagnetic transducer in the head tends to emit electromagnetic interference (EMI) which may tend to interfere with the operation of other electronic devices. Although the disk drive enclosure may be shielded to suppress EMI emitted by the head, such shielding adds to the expense of disk drive enclosures. Even if the EMI is suppressed by a disk drive enclosure, the EMI may still interfere with the electronics contained within the enclosure.
A system and method for the suppression of EMI related to disk read and write operations would therefore be highly desirable.
In a magnetic recording/reproduction device, such as a disk drive test station, in accordance with the principles of the present invention, one or more conductive elements is positioned in close proximity to a head in order to absorb EMI generated by the head as it reads and/or writes data from/to the magnetic media. A head typically includes an electromagnetic transducer that is attached to a head body. The body is formed to fly in very close proximity to the disk surface as the disk rotates xe2x80x9cbeneathxe2x80x9d the head (Although the head may be located above or below the disk, for the clarity and convenience of description, the head will often be referred to as flying above the disk.) The conductive element provides a low impedance path to ground for absorbed EMI, thereby significantly reducing EMI. As used in the context of this document, the term xe2x80x9cgroundxe2x80x9d may refer to any of a number of electromagnetic potentials, such as xe2x80x9csystem groundxe2x80x9d, xe2x80x9cdevice groundxe2x80x9d, xe2x80x9ccabinet groundxe2x80x9d, etc. used as a reference potential and which is generally designed to be at the same potential as earth ground, or earth potential.
The conductive element may be positioned on the opposite side of the disk from the head, on the same side of the disk as the head, or one or more conductive elements may be positioned on each side of the disk. The conductive element may make low-impedance contact with ground though a low-impedance connection to a disk-drive""s loading arm, for example. The conductive element may be positioned in close proximity to the head by forming the element using much the same design and suspension as a flying head and xe2x80x9cflyingxe2x80x9d the conductive element on the opposite side of the medium from the head at approximately the same distance from the disk surface as the head. Alternatively, a xe2x80x9cnon-flyingxe2x80x9d arrangement may be employed whereby the conductive element is positioned futher from the surface of the disk, on the order of a few mils, for example. In such and arrangement, the surface area of the conductive element may be increased, to a multiple of the head""s surface area, for example, in order to compensate for the increased distance and maintain the capacitive coupling efficiency.
A conductive element in accordance with the principles of the present invention may also be formed to operate on the same side of the disk as the head. In such embodiments, the conductive element is placed in close proximity to the head""s transducer in order to capacitively couple EMI created by the transducer. The conductive element may take on many forms. For example, the conductive element may be a small, substantially planar structure suspended between at least a portion of the head and the disk, it may be a structure that substantially envelopes the head, leaving an aperture for the operation of the transducer. That is, the conductive element is formed in close proximity to the head, in such a manner as to allow the read or write portion of the head to operate unimpeded while covering some remaining portion of the head. A conductive element in accordance with the principles of the present invention is particularly useful in a disk testing system that employs a plurality of heads, any number of which heads may be reading and/or writing simultaneously.